Shape of the two-photon-continuum emission from the ${1\mathrm{s}2\mathrm{s}}^1$${\mathrm{S}}_0$ state in He-like krypton

We report a measurement of the spectral distribution of photons from the two-photon decay of the ${1\mathrm{s}2\mathrm{s}}^1$${\mathrm{S}}_0$ level in heliumlike krypton. In the experiment, a beam of ${\mathrm{Kr}}^{34+}$ ions was excited using a thin carbon foil and the two-photon decays were observed as coincidences in an array of x-ray detectors. An important part of this work was the measurement of the efficiency of the detection system as a function of photon energy. A Monte Carlo model of the experiment was used to compare the data with theoretical calculations and demonstrated good agreement with the nonrelativistic calculations for Z=36.